I'm new to xubuntu (only because my laptop won't run any modern linux flavour).[pentium m]
Randomly I would get a keyboard hang up - no warning. (when i say this, a couple of times the menu also did not work)
The mouse still works and if I switch to another tty, the keyboard works fine.
from here I can run an init 6 to reboot the system and all is well again.

I have noticed that it is more prone to happen when I use the keyboad shotcuts on my laptop, for instance fn+vol up or fn+vol down.

I have not installed proprietary ati drivers nor changed keymappings.
updated or unupdated, it does the dame thing. (I have now installed 12 times)